Core-wound paper products are in constant use in daily life. Particularly, toilet tissue and paper towels have become a staple in home and industry. Such products comprises a roll of the consumer goods wrapped in a spiral around a hollow center core. The hollow center core has a a volume which is not used until the product is inserted onto a spindle for dispensing by the consumer.
One factor affecting the pricing and usage of core-wound paper products is the costs of transportation, storage and shelving for such products. These costs reflect the size of the core-wound paper product and are increased by the volume of the core. One attempt in the art to reduce the costs associated with the contribution of the package volume to the size of the core-wound paper product is to compress the product, reducing or eliminating the void space of the hollow core.
For example, as early as 1889, U.S. Pat. No. 401,233 issued Apr. 9, 1889 to Wheeler disclosed a flattened roll of toilet paper having a comparatively rigid interior reinforcement. This arrangement is to allow the incisions, which facilitate insertion of a suspensory device, to lie in the same plane. As early as 1911, U.S. No. Pat. 1,005,787 issued Oct. 10, 1911 to Sibley disclosed a corrugated core for packages of wound fabric. The package is compressed into a flattened state to occupy less space during transportation and stocking. U.S. Pat. No. 1,316,041 issued Sep. 16, 1919 to Johnson disclosed a straight flattened roll of toilet tissue having a core of flexible material with overlapped ends. The flat state was used for shipping, then the roll was bent into a kidney shape for application onto a dispensing fixture.
Compressed core-wound paper product was also used in World War II, per government specifications. As described in the May, 1944 edition of Tissue Topics, the Hoberg Paper Mills Company intra-company newsletter, government toilet tissue was collapsed or flattened and packed in 1,000 sheet rolls with 60 rolls per case. This arrangement was said to have conserved enough space to account for nine months of movement of a Liberty class cargo ship.
One problem associated with compressed core-wound paper products is that of rerounding the cores to a generally cylindrical shape having a circular cross section. Rerounding is necessary to allow a spindle to be inserted through the core, so it can be used on an ordinary dispenser. Rerounding is often effected, as disclosed in U.S. Pat. No. 4,909,388 issued Mar. 20, 1990 to Watanabe, by applying lateral compressive forces to the sides of the compressed core-wound paper product.
When lateral compressive forces are applied to the product, the opposed sides of the core are expected to pop outwardly and away from each other. Each half of the core is then oriented concave towards the center of the core and the other half. However, frequently both halves of the core will buckle in the same direction, forming a somewhat crescent-shaped cross section. This phenomenon is known as core inversion and occurs when both sides of the core buckle such that the two halves of the core are concave in the same direction.
When core inversion occurs upon rerounding, it is very difficult for the consumer to insert the spindle through the opening in the center of the core. The opening is too small to freely admit the spindle and the opposed halves of the core do not readily expand outwardly to be concave in opposite directions once inversion has occurred.
However, the prior art related to compressed core-wound paper products has done little, if anything, to address this phenomenon. For example, commonly assigned U.S. Pat. No. 5,027,582 teaches away from the present invention by disclosing a method of packaging a compressed core-wound paper product by flattening the rolls, securing the flattened rolls to preclude substantial expansion, then relieving the loading used to flatten the rolls.
Other art teaches away as well. For example U. K. Patent Application 709,363 published May 19, 1954 in the name of Samson teaches diametrically flattening the cores and product. U.S. Pat. No. 4,909,388 issued Mar. 20, 1990 to Watanabe teaches flattening the roll product to one-half its original volume or less and maintaining the roll in a particular flattened shape. This patent further teaches that rerounding occurs due to crepes and embosses in the paper product.
One attempt in the art to promote rerounding is found in U.S. Pat. No. 4,762,061 issued Aug. 9, 1988 to Watanabe et al. This patent teaches flattening the paper product through multi-stroke bilateral compression will improve the capability of the core-wound paper product to properly reround.
However, it has been found that rerounding is greatly improved and occurrences of core inversion are obviated if the core is not presented to the consumer in a flattened state--as taught by the aforementioned art. Instead the compressed core-wound paper product should be presented to the consumer with the opposed sides of the core slightly opened and spaced apart from each other as specified below. The size of the opening should not be too small, otherwise the congenital inversion failures noted in the aforementioned prior art will still appear. Conversely, the size of the opening should not be too great, otherwise, in addition to defeating the desired economies of space savings, the core-wound paper product will appear to be product which has been inadvertently damaged, rather than deliberately compressed to a slight degree. Such appearance may evoke a negative consumer reaction without providing an offsetting benefit of economization.
Cores for core-wound paper products having an opening are taught in the aforementioned U.S. Pat. No. 1,005,787 issued Oct. 10, 1911 to Sibley. This patent discloses a corrugated core which is somewhat elastic, yet either flexible or yielding. However, this patent does not teach the relationship between the corrugated core and the material wound thereon necessary to achieve a core opening which minimizes core inversions. Instead this patent simply teaches that the relationship between the core and the material wound thereon should permit the core to be inserted into the packages after the rolls are expanded, so that no difficulty is experienced in changing the roll shape. Clearly the step of inserting the core after expanding the product is an added inconvenience most consumers would find unacceptable.
It is an object of this invention to improve the ability of the consumer to reround, with fewer occurrences of core inversion, the core of a compressed core-wound paper product to a generally cylindrical shape having a circular cross section. It is an object of this invention to produce a compressed core-wound paper product which encounters reduced occurrences of core inversion when the consumer attempts to reround the core to a generally cylindrical shape having a circular cross section.